Breaking down mechanism



April 1946. I C. E.,TIBBALS 2,399,074

BREAKING DOWN MECHANISM Filed June 15, 1945 7 Sheets-Shee t 1 Inventor a /e6 f. 7;; 1361/6.

y w m WWW Em April 1 I c. E. TIBBALS 2,399,074

BREAKING DOWN MECHANISM Filed June 13, 1945 '7 Sheets-SheetZ Inventor cam/e6 Anya/6.

April 23, 1946 c. E. TIBBALS BREAKING DOWN MECHANISM Filed June 13, 1945 7 Sheets-Sheet 3 I m entor Cz'zanfesf. $560116.

. Q 8 m ww P 1946. c. E. TIBBALS BREAKING DOWN MECHANISM Filed June 13, 1945 7 Sheets-Sheet 4 Inventor adrksf: 7125:1155.

daf -3% v Attorneys April 1946. c. E. TIBBALS BREAKING DOWN MECHANISM Filed June 13, 1945 '7 Sheets- Sheet 5 ull Czar/ea E Z'afj.

Patented Apr. 23, 1946 UNITED STATES PATENT OFFICE,

2,399,074 BREAKING DOWN MECHANISM crimes n. Tibbals, Bluefield, W. Va. Application June 13, 1945, Serial No. 599,259 11 Claims. 01. 262-9) This invention relates to an improved mechanism for breaking down coal after undercutting the same, and more particularly to a breaking down mechanism especially adapted for use in connection with an entry driving machine of the type disclosed in my co-pending application for U. S. Letters Patent Serial No. 548,768; filed August 9, 1944, wherein the undercutting is performed by means of a pair of overlapping segmental undercutters rmounted to oscillate about vertical axes and at the forward end of the machine.

Production of coal by means of an entrydriving machine of the type shown in my above-mentioned co-pendin'g application, is limited by the speed at which the breaking down mechanism can break down the coal for being conveyed from theworking face.

The primary object of the present invention, therefore, is to provide a breaking down mechanism by means of which the coal may be expeditiously broken down from the Working faceand thereby providing for a maximum of coal production for a given period of time.

Another object of the present invention is to provide a breaking down mechanism by means of which a comparatively large percentage of the coal can be broken down in lumps of larger size than can be obtained by the use of mechanical picks alone.

Specifically, the present invention contemplates the provision of breaking mechanism comprising a unit mounted to swing in an are about a vertical axis and including a vertical battery of projectable and re'tractible compressed air operated pick devices having breaking down wedges, and a vertical gang of projectable and retractible drills arranged to operate in advance of the pick devices so as to provide holes in the face for the respective wedges to readily enter, thereby facilitating the breaking down action of the pick devices and positioning of the pick devices to break down lumps of coal of maximum size.

A further object of the invention is to provide an entry driving machine having oscillating undercutters, and wherein a breaking down mechanism of the present kind is associated with each undercutter and includes a breaking down unit mounted to swing about a vertical axis coincident with the axis of the associated undercutter.

Still another object of the present invention is to provide a breaking down device including a wedge adapted to be driven by power into a drill hole adjacent and substantially parallel with a free face of the coal, and a hinged bit which is forced laterally toward the free face from adja cent the bottom of the drill hole to aid the wedge in completing the breaking down operation for substantially the full depth of the drill hole.

Yet another object of the present invention is to provide effi'cientme'ans for mounting and driving the gang of rotary'drills forming part of the breaking down uniti v a Other and more specific objects and features of the present invention will become apparent from the following description when considered in connection with the accompanying drawings,-

in which: a

Figure 1 is a top plan view of an entry driving machine embodying breaking down mechanisms constructed in accordance with the present invention.

Figure 2 is an enlarged fragmentary vertical longitudinal section taken substantially on the line 2 -2 of Figure 1. V

Figure 3 is a view similar to Figure 2 taken on line s e of Figure 1.

Figure 4 is a section taken on line 4" l of Figure'2.

Figure 5 is a view similar to Figure 4, but with the drills and pick devices retracted.

Figure '6 is an enlarged detail view, breken wa Figure '4. I a

V Figure 7 is a view similar to Figure 6, but with the bit of the pick retracted.

Figur'eB isa fragmentary view, partly in section and partly in plan of one of the drills and associated parts, the drill being retracted.

Figure 9 is an enlarged section taken on line Ball of Figure 8. a

Figure 10 is an enlarged fragmentary section taken on line 3-49 of Figure 3.

Figure 11 is a view similar to Figure 10, but with the partsretracted. l.

Figure 12 is an enlarged section taken on line 2 4 '2 of Figure 10. 7

Figure 13 is an enlarged section takencn line partly of one of the picks as shown in B543 o'fFigure 11.

Figure '14 is an enlarged fragmentary section taken on line 14-44 of Figure 3'.

Figure 15is a diagrammatic view of the working'face, illustrating a modifiedmanner of arranging certain drills and picks of the breaking down unit in laterally offset relation to .the remaining drills and picks thereof so that, when a band of slate or other hard material occurs in the coal vein, such slate or like hard material may be readily broken down; one of the undercutters being shown in section.

' conveyor I.

The present breaking down mechanism is particularly designed to form part of an entry driving machine including a shaking conveyor I, of a well known type, consisting of a trough composed of a series of connected sections and longitudinally reciprocated by conventional means so as to have a rapid forward movement and a relatively slower rearward movement for causing rearward travel of the coal as it is broken down and fed onto the shaking conveyor. As this type of conveyor is old and very well known in the art, it is only indicated and described as to type, and need not be detailed herein.

A telescoping conveyor section 2 is fitted to the forward end of the conveyor I, and two horizontal segmental or substantially semiecircular undercutters 3 and 4 are operatively connected to the conveyor section 2 so as to be simultaneously oscillated in opposite directions by the shaking The major portions of the undercutters contact the mine floor, but they overlap at adjacent sides, there being a direct pivotal connection -5 between the inner side of the undercutter 3 and the conveyor section 2, and a link connection 6 between the inner side of the undercutter 4 and the conveyor section 2. Removable bits I are provided On the arcuate edge of each undercutter, and the undercutters are pivoted at their center pointsS to oscillate about vertical axes aligned transversely of the machine. The forward end of conveyor section 2 extends between the adjacent overlapped portions of the undercutters 3 and 4, and disposed at opposite sides of the forward end of conveyor section 2 are rigidly connected hollow base members 8 whose rear portions restupon the mine floor and which have forward portions that are spaced from the mine floor and have the rear central portions of the undercutters 3 and 4 extended thereunder for pivotal mounting at the center Points 9. As the shaking conveyor reciprocates, it causes the semi-circular undercutters 3 and 4 to oscillate about the center points 9 for a distance slightly more than that between adjacent bits 1. The undercutters are provided near their center points with raised portions 3a and 4a to aid in keeping the coal near the outer edges of said undercutters. The pivots for the undercutters 3 and 4 embody ball and socket joints indicated at 25, and these joints permit a desirable flexibility by allowing the undercutters to have limited movement relative to the base members 8 for assuming diiferent angular positions relative to the latter and thereby maintaining fiat engagement with the floor as well as sliding over irregularities of the floor surface. The assembly or unit composed of the elements 2, 3, 4 and 8 is fed forwardly by feed screws I2 to bring the undercutters 3 and 4 into position for making a new undercut, until the conveyor section 2 is sufficiently extended to permit the insertion of another shaking conveyor section between the foremost section of said conveyor I which is illustrated and the conveyor section 2. The feed screws I2 are rotated by pawls I4 carried by and movable with the undercutters 3 and 4 and engaging ratchet wheels I3 secured on the'feed screws I2 within the base members 8. The ratchet wheels I3 protrude through the tops of the base members 8 for engagement by the pawls I4, and the forward ends of thescrews I2 are suitably journaled in the base members 8. The feed screws have threaded engagement in thread boxes provided in the bases of screw jacks I'I disposed at opposite sides of the conveyor section 2 and engaged with the roof and floor of the mine. The assembly is maintained in alignment with the conveyor I and midway between the sides of the entry by guides I9 arranged to engage the opposite side walls of the entry and hinged to the base members 8 as at 22 so that they may be swung to either a vertical inoperative position or to a horizontal operative position.

The guides are extensible and retractible into or out of proper engagement with the side Walls of the entry, and they include wheels 20 arranged to run in the plane of the kerf 23 cut by the bits of the undercutters 3 and 4.

As the machine feeds forwardly, the bits of the undercutters out the kerf 23 in the coal so as to provide an undercut. The undercut portion of the coal is broken down onto the undercutters and fed by the latter rearwardly on to the conveyor section 2 which transfers it to the conveyor I for delivery to the desired point away from the working face of the entry. The conveyor section is periodically extended by the machine operator, and new sections or pans for the conveyor I are inserted as needed. Thus far described, the machine is substantiall that disclosed in my above mentioned co-pending application, and the undercut coal is broken down on to the undercutters by means including a vertical battery of picks associated with each undercutter and mounted to swing in an are about a vertical axis coincident with the pivotal axis of the associated undercutter.

The present invention has particular reference to improved'means for breaking down the undercut coal on to the undercutters 3 and 4. A breaking down means or mechanism is associated with eachundercutter, and as both breaking down mechanisms are alike, description of one will suifice for both. A battery of compressed air operated pick devices 29 is mounted over each undercutter so as to rotate about the center point 9 of the latter, the pick devices of each'battery being disposed one above the other in forwardly diverging relation. The pick devices are mounted on the inner side of a vertical frame or plate 30 which has vertically aligned stub shafts 3i and 3Ia adjacent its rear end respectively journaled in bearings of a brace 32 fixed on the adjacent base member 8 and in the forward end of the adjacent base member 8. The lower shaft 3Ia is rotated by means including a gear 33 secured on the lower end of shaft 3Ia, a rack 34 meshing with the gear 33 and fixed to the piston rod 35 of a compressed air motor 0 of the reciprocating type. Supply of compressed air to and exhaust of the same from the motor 0' may be controlled in any suitable way.

The compressed air operated pick devices are forced forwardly and retracted by the piston rods of compressed air operated reciprocating motors C2, compressed air for operation of the pick devices being conveyed through the pistons and the hollow piston rods 3'! of the motorsCZ. The pick devices move, in sleeve supports 38 which are mounted on the frame or plate 30, and swinging movementof the frame or plate 33 about the axes of shafts 3I and 3Ia is controlled by pawls or levers 39 and 48 which alternately engage the ratchet wheel 42 journaled on shaft 3Ia, to permit a single-tooth movement each time the pick devices are retracted. A pawl 63 prevents rotation of the ratchet wheel 42 when a cut is being made,

it being understood that the batteries of pick devices are swung away from each other inf-the breaking down operation. a i

ago-co ra 3 and are fed forwardly or backwardly. A col- Compressed air enters at the rear end of each motor C2 to force the piston thereof forwardly and thereby project the pick devices to the position of Figure 2. The compressed air also passes through the hollow piston rods 31 into the motor cylinders of the pick devices 28 foractuatin'g the latter. The compressed air motors of the pick devices are not shown in detail, as they are of well known construction and commonly employed for analogous purposes. In other words, each embodies a rapidly reciprocating piston, and is such as is used in connection with tools for riveting, drilling and the like. When compressed air is cut oif from the rear ends of the motors "C2 and is admitted to the forward ends thereof, the pick devices are retracted from the position of Figure 2'.

A vertical gang of drills 50 is provided on the outer side of the frame or plate 30 to drill a plurality of holes in the coal face in advance of and in spaced relation to the pick devices 28, the number of holes drilled depending upon their spacing and the height of the vein. E'ach drill has a drive gear 5| in which is slida-bly keyed a shaft 52, the hub of the gear being journaled in bearings of a frame 53 mounted on the plate 30. When the shaft 52 is rotated, it is fed forwardly by a thread box housed in a frame 5d attached to the plate 38 as more clearly shown in Figures to 13; in= clusive, the thread box being arranged to engage or release from the threads of the shaft 52 when predetermined limits of movement are reached. Thread blocks '55 are held in slidable blocks 56 by screws 57 so that the thread blocks can be removed when desired, said thread blocks being lar H on shaft 68 keeps the bearing 89 in place.

. As shown in- Figure 3, the drive gears 5| for the several drills mesh with each other so that when one is driven the others are driven thereby so as to alternately drive the'drills in opposite directions. In accordance with this, the drills are held against shaft 52 by springs 51 and being I released bywedge-shaped pieces 58. Guides 59 on the outer sides of the pieces 53 engage in grooves of the box 54. A sleeve 65 is loosely keyed on the shaft 52 so that when the end of keyway 6| in shaft 52 is reached, the sleeve 80 is forced forwardly against a circular member 62 which carries the wedge-shaped pieces 58, thereby causing the wedge-shaped pieces 58 to release the thread blocks 55 from the shaft 52 as shown in Figure 12. This stops the forward feed of shaft 52, but permits continuedrotation of the latter to remove excess cuttings from the holes being drilled in the coal.

' A lug 83 is attached to the rear end of each pick 29 and extends through a'slot 84 in the plate 30, said lug extending around the shaft'5'2 so as to engage a circular member 85 which is secured on shaft 52. Thus, when the picks are retracted, the lugs 53 cause the drill assemblies to also be retracted. As each lug 63 moves rearw'ardly, it causes the associated member 65 to engage the wedge-shaped pieces 58 and force them rearwardly so as to permit thread blocks 55 to be engaged with the shaft 52 by the action of springs 51'. The shaft 52 is not rotated when the pick devices and drills are retracted. Shaft 52 is connected to an intermediate shaft 66 by a universal joint or flexible coupling 51 and shaft 66 is connected to the shaft 68 of the associated drill 50 by means of a similar joint 81' as shown more clearly in Figures 5 and 8. This permits the hole to be drilled in the coal at a proper angle to receive the wedges of the breaking down mechanism when it is swung to a position in front of the hole. As shown in Figure 8, the drill shaft 68 is journaled in a bearing 89 slidably mounted in guides 10 attached to the plate as shown in Figure 9, so that bearing-89 can move as the shafts 5'2, 6'5

alternately of right and left hand form so that they may simultanously perform drilling of holes. The drive gear 5| of-one drill meshes with a pinion 1'2 journaled in a case 13 fixed to the frame 53 as shown more clearly in Figure 14, the pinion l2 meshing, in turn, with a further pinion I4 disposed in the case 13 and fixed on the armature shaft 15 of an electric motor 16 fixed to a base plate '71 suitably secured to frame 53 and the adjacent thread box 54. An auger drill has its shank fitted in the forward end of shaft 88 as at 18 (Figure 8). is used when the latter are being fed forward into the coal, but not when the drills are being retracted nor when the assembly or breaking down unit is being swung to a new position outwardly of the free face 19 created by the previous breaking down operation. It will be noted that the forward end of plate 30 is bent at a. slight angle laterally and outwardly from the picks "29 so that the drills are located at the proper angle to and spaced the desired distance from the pick devices. In this way, the holes can be drilled in the coal at most suitable distance from the free face 19 being produced by the pick devices whereby to break down the coal in lumps of maximum size when the pick devices are swung to operate in the next set of holes formed by th drills.

Each pick device 29 includes a hollow piston rod 80 on the forward end of which is fixed a wedge-member 8| whose forward end is sumc'iently'small to enter and snugly fit in a hole made by one of the drills 58. A coil spring 82 is provided within wedge member 8| and yieldingly acts to project a member 83 slidably mounted in and extending through the forward end of wedge member 8|. Pivoted to the forward end of wedge member 8| and disposed to enter a longitudinal slot of the sliding member 83 is a hook-shaped bit 84 that is normally held in the slot of member 83 by means of a spring 85. The slot of member 83 has a beveled or oblique wall at 88 at its outer end which is engaged by the outer free end of the bit 84, for a purpose which will be presently explained, Pick bits 81 are rigidly mounted on the top and bottom of the wedge member 8| and project beyond the forward end of the latter to split the coal between the drilled holes. When the compressed air motors C2 are operated to project the pick devices 29, the wedge and bit assemblies of said devices are vibrated or are rapidly reciprocated and the wedge members 8| and the bits 81 are forced into the coal, dislodging it. The coal is initially dislodged for part of the depth of the undercut and of the drilled holes. As the wedge and bits 81 approach points adjacent the bottom of the drilled holes, the sliding member 83 is forced rearwardly against the action of spring 82 and the beveled wall 86 of the slot in member 83 causes the pivoted bit 84 to swing laterally out of said slot and break the coal off where it solidly joins with the portion of the coal which has not been drilled or undercut. This action is clearly illustrated in Figures 6 and 7, and the coal is effectively broken down for "the full depth of the drilled holes and the undercut. The action of the supplemental The drive for the drills hinged bit 84 is important because the wedging action of the wedge member 18! and the. splitting action of the'bits 81 are insufficient for effective and complete breaking down of thecoal for the full depth of the drilled holes. The sliding member 83 has a stem provided with a transverse hole at 81', and slidable transversely of the rod 86 is a bolt 88 actuated by a bellcrank lever 89 pivoted on the rod 80 and a trip rod 90 pivoted at one end to lever 89 and extending rearwardly and slidably through a guide 9| secured to the forward end of the adjacent pick cylinder. Lever 89 is actuated to project the bolt 88 into the hole at 8], by means of a spring 92. When the sliding member 83 reaches its rearward limit of movement as shown in Figure 6, the bolt 88 is projected into the hole 8'! by spring 92, thus locking the hook-shaped bit 84 in its laterally projected or extended position. When the pick devices 29 are retracted, the bits 84 pull the coal away from the face. As the assembly is retracted, rod 99 engages sleeve 38 and actuates lever 89 to release bolt 88 from the stem of sliding member 8?. Spring 82 then projects member 83 and spring 85 holds bit 84 in its retracted position within the slot of member 83 as shown in Figure ,7, the portion of member 83 at the inner end of. its slot acting to swing the bit 86 back to the position of Figure 7 from the position of Figure 6. Exhaust air from the cylinder of pick device 29 can be conveyed through the hollow rod 80 into the wedge and bit assembly to dislodge dust and fine coal and prevent it from clogging the movable parts of said assembly.

Obviously, step by step swinging movement of the plate at maybe effected by actuation of the motor C at suitable intervals so as to position the mechanism for breaking down coal along the line of the drilled holes formed adjacent the pick devices 29 engages levers. 39 and and permits the breaking down mechanism to swing the required distance to assume the new break-v ing down position. While the motors C and C2 may be manually controlled they may be automatically actuated in the manner and by the means disclosed in my above-mentioned copending application. The batteries of pick devices and gangs of drills swing independently of the undercutters 3 and 4, so that they can be given the desired step by step movement for successively moving into new positions for breaking down the coal as each new set of free faces is established. As shown in Figure 15, a hard stratum S of slate or other foreign material which cannot be readily cut or drilled, occurs in many coal veins. When this condition occurs, the upper portion of plate 30 may be offset laterally relative to the lower portion thereof so as to correspondingly offset the upper pick devicesand' drills relative to lower ones thereof. In this way, the holes 95 made by the upper drills will be offset laterally with respect to the holes 95' formed by the remaining lower ones of the drills, respectively, above and below the stratum 94. This provides a drill hole directly over the hard stratum and in the coal at a point above the portion of the stratum 94 which is unsupported by the coal because the latter has then'dislodged from beneath the same. Thus, the wedge and bit assembly operating in the drilled hole directly above the stratum may effectively break down the portion of such stratum projecting beyond that portion of the free face 19 below the stratum 94. The upper pick devices being correspondingly ofiset, each time the free face 19 is formed, its upper portion will be offset laterally with-respect to its lower portion, respectively above and below the stratum 94, as shown in Figure 15. This change merely involves the provision of an offset in plate 30 at the proper height, and an intermediate gear between the drive gears for the drills which form holes respectively directly above and below the stratum 94.

From the foregoing description, it is believed that the construction, operation and advantages of the present invention will be readily understood and appreciated by those skilled in the art. Minor changes may be made in details of construction illustrated and described, such as fall within the scope of the invention as claimed.

What I claim is:

1. In an entry driving machine, breaking down mechanism comprising a laterally movable vertical frame, a vertical battery of pressure operated pick devices slidably carried by said frame for projection toward and retraction from the working face, power operated means for projecting and retracting said pick devices, said pick devices including breaking down wedges, a vertical gang of auger drills carried b said frame for feeding toward and retracting from the working face and arranged to form holes in the face in advance of the pick devices for the breaking down wedges to enter when the pick devices are moved laterally and then projected, driving means for said drills, releasable feeding means to feed the drills toward the working face when the drills are driven, and means to automatically release said feeding means to permit retraction of the drills after the latter have been fed forwardly a predetermined distance.

2; The construction defined in claim 1, in combination with a laterally swinging pick bit normally aligned with and carried by the forward end of each wedge, and a spring projected member carried by each wedge and engageable with the bottom of a drilled hole for being forced rearwardly as the hole is entered by the wedge, said spring projected member embodying means to swing said bit laterally and break the coal down near the bottom of the drilled hole when said member is forced rearwardly.

3. The construction defined in claim 1, in combination with a laterally swinging pick bit normally aligned with and carried by the forward end of each wedge, and a spring projected member carried by each wedge and engageable with the bottom of a drilled hole for being forced rearwarclly as the hole is entered by the wedge, said spring projected member embodying means to swing said bit laterally and break the coal down near the bottom of the drilled hole when said member is forced rearwardly, locking means to automaticall lock the spring projected member in its rearward position and thereby hold the swinging bit in its laterally swung position when said wedge reaches a predetermined position in the drilled hole, and means to automatically unlock said locking means when the associated pick devices approaches its fully retracted position.

4. The construction defined in claim 1, in combination with means to automatically retract the drills when the pick devices are retracted, and means to automatically render the drill feeding means operative when the pick devices and drills V in the driving means for the drills includes intermeshing gears journaled in fixed positions on the frame, drive shafts slidably keyed in said gears, and a motor mounted on the frame for driving one of said gears, said drill being alternately of opposite pitch.

6. The construction defined in claim 1, in combination with means to laterally move said frame, and means to limit movement of the frame each time it is moved laterally so as to dispose the wedges to enter the drilled holes already formed by the drills in advance of the pick devices.

7. In combination with an entry driving machine having overlapping horizontally oscillated segmental undercutters, a breaking down mechanism associated with each of said undercutters, each breaking down mechanism including a vertical frame mounted above the associated undercutter to swing horizontally about an aXis coinci-- dent with the axis of oscillation of the latter, a vertical battery of pressure operated pick devices slidably carried by said frame for projection toward and retraction from the working face, power operated means for projecting and retracting said pick devices, said pick devices including breaking down wedges, a vertical gang of auger drills carried by said frame for feeding toward and retracting from the working face and arranged to form holes in the face in advance of the pick devices for the breaking down wedges to enter when the pick devices are moved laterally and then projected, driving means for said drills, releasable feeding means to feed the drills toward the working face when the drills are driven, means to automatically release said feeding means to permit retraction of the drills after the latter have been fed forwardly a predetermined distance, means to normally hold the frame against swinging and automatically operable to permit and limit swinging movement thereof for the proper distance to dispose the wedges to enter the drilled holes already formed by the drills in advance of the pick devices when the drills and picks are retracted, and means to swing the frame.

8. In a breaking down mechanism, a frame, a pressure operated pick device slidably carried by said frame for projection toward and retraction from the working face, power operated means for projecting and retracting said pick device, said pick device including a breaking down wedge, an auger drill carried by said frame for feeding toward and retracting from the working face and arranged to form a hole in the face in advance of the pick device for the breaking down wedge to enter when the pick device is moved laterally and then projected, driving means for said drill, releasable feeding'mean to feed the drill toward the working face when the drill is driven, and means to automatically release said feeding means to permit retraction of the drill after the latter has been fed forwardly a predetermined distance. i

9. The construction defined in claim 8, in combination with a laterally swinging pick bit normally aligned with and carried by the forward end of said wedge, a spring projected member carried by said wedge and engageable with the bottom of the drilled hole for being forced rearwardly as the hole is entered by the wedge, said spring-projected member embodying means to swing said bit laterally and break the coal down near the bottom of the drilled hole when said member is forced rearwardly.

10. The construction defined in claim 8, in combination with a laterally swinging pick bit normally aligned with and carried by the forward end of said wedge, a spring projected member carried by said wedge and engageable with the bottom of the drilled hole for being forced rearwardly as the hole is entered by the wedge, said spring-projected member embodying means to swing said bit laterall and break the coal down near the bottom of the drilled hole when said member is forced rearwardly, locking means to automatically lock the spring-projected bit in its laterally swung position when said wedge reaches a predetermined position in the drilled hole and means to automatically unlock said locking means when the associated pick device approaches its fully retracted position.

11. In a breaking down mechanism, a frame, a pressure operated pick device slidably carried by said frame for projection toward and retraction from the working face, power operated means for projecting and retracting said pick device, said pick device including a breaking down wedge,

an auger drill carried by said frame for feeding toward and retracting from the working face and arranged to form a hole in the face in advance of the pick device for the breaking down wedge to enter when the pick device is moved laterally and then projected, driving means for said drill, releasable feeding means to feed the drill toward the working face when the drill is driven, and means to automatically release said feeding means to permit retraction of the drill after the latter has been fed forwardly a predetermined distance, means to automatically retract the drill when the pick device is retracted, an means to automatically render the drill feeding means operative when the pick device and drill approach their fully retracted positions.

CHARLES E. TIBBALS. 

